Electric lamp for producing modulated lights



.July 14, 1936- H. BRASELTON;

ELECTRIC LAMP FOR PRODUCING MODULATED LIGHTS Filed Aug. 25, 1932 3Sheets-Sheet 1 INVEN' I'OR y 1935- c H. BRASELTON 2,047,175

ELECTRIC LAMP FOR PRODUCING MODULATED LIGHTS July 14,1936 c. H. BRAsELoN ELECTRIC LAMP FOR PRODUCING MODULATEDLIGHTS Filed Aug. 25, 1932 3Sheets-Sheet 3 Patented July 14, 1936 UNITED STATES PATENT OFFICEELECTRIC LAMP FOR PRODUCING MODULATED LIGHTS Chester H. Braselton, NewYork, N. Y., assignor to Sirian Lamp Company, Newark, N. J., acorporation of Delaware Application August 25, 1932, Serial No.-630,3783 Claims. (Cl. 116-122) This invention relates to electric lightingdevices of the type which produces a modulated light for use especiallyin devices necessitatin very rapid changesof intensity such astelevision receiving apparatuses.

One of the objects of the invention is to provide a modulated light inwhich the energy source for supplying the illumination is independent ofthe incoming wave signal.

Another object of the invention is to provide a modulating electriclight in which a gaseous Several embodiments of the invention have beenillustrated in the accompanying drawings in which:

Figure 1 is a sectional side elevational view of one form of lampembodying the invention; Fig. 2 is a front elevational view of theelements of Fig. 1;

Fig. 3 is a sectional plan view of the elements connecting the cathodeof the structure of Fig. 1;

Fig. 5 is a sectional side elevational view of the elements of anotherembodiment of the invention;

Fig. 6 is a front elevational view of the elements of Fig. 5;

Fig. 7 is a sectional rear elevational view of still anothermodification of the invention;

Fig. 8 is a. sectional side elevational view of the elements of Fig. 7;

Fig. 8a is a detail view in perspective of a slight modification of thecontrol electrode of Fig. 8; l

Fig. 9 is a planview of the structure shown in Figs. 7 and 8;

Fig. 10 is a sectional side elevational view of still another embodimentof the invention;

Fig. 11 is a front elevational view of the elements of Fig. 10;

Fig. 12 is a sectional plan view of the construction of Fig. 10 taken onthe line l2-l2 of that figure:

Fig. 13 is a perspective view of one of the shields shown in Figs. 10and 11; and- Fig. 14 is'a plan'view of the elements of Figs. 10 and 11.

Referring now more specifically to the drawings the invention is shownin Fig. l as comprising a bulb ill of transparent material such asglass, quartz, or the like with a press ll formed integral with thebottom of the bulb and extending upwardly inside thereof in the usual.manner of forming electric lamps. The press II,

however, is preferably provided with a circular enlargement I2 adjacentthe center thereof 15 the top of which is flush with the top of thepress ii and the purpose of which will be evident as the descriptionproceeds.

A tubular cathode I 3 formed of nickel or other suitable material andcoated on its surface with electron emitting material It is mountedvertically adjacent the center of the bulb upon an insulating member l5which has a hole It extending through it with a shoulder l1 toreceivethe'lower end of the cathode. The electron emitting material l4 may beany of the well known materials used for that purpose such as the oxidesof the alkaline earth group of metals.

ormixtures of such oxides held together with a suitable binder. Themember I5 is preferably provided with a depending peripheral flange [8which may rest upon the press H and if desired a suitable rim I 9 may beprovided on the press I I at the central portion to secure theinsulating member i 5 in position on the top of the press and preventhorizontal displacement thereof. member l5 may be made of any suitableinsulating material such as quartz vitreous insulators, or the like, andpreferably one which is opaque so as to prevent any light rays frompassing through it.

A housing formed of similar material in the shape of ahollow cylinderhaving a diameter slightly larger than the insulating member I5 isplaced thereover to rest upon the top of the press H. The housing 20 maybe held in position upon the press i I by means of a pair ofsemi-circular clamps 2| which surround the housing at' the bottomthereof, resting upon a shoulder 22 provided for that purpose in thehousing, and are welded to two short support rods 23 which are The upperend of the tubular cathode. This housing holds the cathode securely downupon the insulating member i3 and the insulating member l3 down upon thepress II.

A pair of short connecting rods 21 may be mounted in the press I l atthe center thereof being short enough to terminate under the insulatingmember l3 and to these rods I weld or otherwise secure the ends of ahairpin filament 23 which extends up through the inside of the cathode,the loop end terminating in a cavity 33 provided for that purpose in theupper wall 23- of the housing 23. The filament 23 may be coated with asuitable insulating material so as to prevent short circuiting betweenthe adjacent legs of the filament and between the filament and cathode.

' Electrical connection may be made to the cathode l3 by means of a band30 of metal which may be welded around the lower end thereof with itsends bent out radially from the cathode. and these ends may be welded toa rod 3| which is sealed in the center 'of the press i I between theconnectors 31 and which may be bent outwardly and upwardly to reach theband 30, passing through a suitable groove 32 provided in the insulatingmember l3 as shown in Fig. 4.

A control electrode 33 which may be formed of a spiral coil of wire, asshown in Figs. 1 and 2, or which may be formed of wire mesh or merely aflat metal plate, as desired, is provided with a hole or open space 33and may be positioned ad- Jacent the housing being mounted on a supportrod 33 which is also sealed in the press II. The housing 23 adjacent thecontrol electrode 33 is provided with a hole 33 which may have anyconfiguration depending on the configuration of the light desired, thehole 33 being preferably somewhat smaller than the opening 33.

On the outside of the control electrode 33 I provide a plate 31 whichmay be formed of nickel if desired although highly refractory metalssuch as tungsten and molybdenum may be used. The plate 3! acts as theanode for the device and is provided with a hole 33 in the centerthereof which is preferably larger in diameter than the opening 33 inthe grid 33 as the illumination in the opening 33 in the housing 20 isto be observed through the hole 33 in the anode. The anode may besupported upon a support rod 33 also sealed in the press II. In order tomake the electrical connections to the device a pair of wires 33 may beconnected to the filament connectors 21, while a wire 3| may beconnected to the cathode connector 3i. Similarly a wire 32 may beconnected to the control electrode support rod 33 and a wire 33 may beconnected to the anode support rod 39.

With the elements thus assembled the bulb may be connected in the usualmanner to a vacuum pump and an oven placed over it to raise thetemperature of the bulb and associated parts while the pump isexhausting the air and other gases which may be present. During thistime the filament is energized by passing a current through it so as toraise its temperature and heat up the associated parts, and as much ofthe occluded gases and vapors are removed from the elements of thedevice as possible. when all of the gases have been removed a smallamount of ionizable gas suchas neon may be admitted at a pressurepreferably under mm. of mercury. Other gases may be used such as argon,helium, krypton, and zenon, or mixtures of such gases, the monatomicgases being preferred. Also metal vapors, such as the vapors of mercury,caesium, and rubidium may be added to increase the conductivity of thegas and for color effects. The lamp may then be sealed off and is readyfor use.

When the lamp as described is completed it may be connected in a circuitas indicated in Fig. 1. Thus the two filament leads 3! may be connectedto the secondary 33 of a transformer 33, the primary 33 of which isconnected to the source of alternating current supply. The wire 32connected to the control electrode may be connected to the input circuit31 which carries the incoming signal, the other side of the inputcircuit being connected through the biasing battery 33 to the cathodeconnecting wire 3|. A B battery 33 or other source of plate potentialmay have its negative side also connected to the cathode lead wire 3|while the positive side may be connected to the wire 33 which forms theanode connector 20 there is a difference in potential between the 25anode and the cathode, electrons will move from the cathode to the anodebut inasmuch as the housing 23 surrounds the cathode and shields it fromthe anode at all points, except at the opening 33 in the wall thereof,all of the electron stream will tend to pass through this opening inorder to reach the anode. Inasmuch as the lamp is filled with anionizable gas the gas is ionized by this electron stream and the resultis an intense illumination appearing in the hole 36 as the ionicdischarge passes through it to reach the plate. Similarly to the actionof a vacuum amplifying tube the negative charge on the control electrodewill tend to repel the discharge and cause it to return to the cathode,while a positive charge on the control electrode will speed thedischarge on its way toward the anode,

- and thus variations of the potential of the control electrode causedby the incoming signal will vary the density of the discharge. Inasmuchas there is a hole 38 in the anode an observer can stand in front of theanode and look through it and through the opening 33 in the controlelectrode at the hole 36 which, as has been said above, will appearintensely bright as long as the control electrode is positively chargedor at zero potential, and the illumination will fade out as the controlelectrode builds up on the negative side. 'i

Such a lamp is especially desirable for use in television reproducingapparatus where a spot of modulated light is caused to move across thefield of vision in any one of a number of different ways which are nowthe subject of considerable research and experimentation.

For use with certain types of television devices it may be desirable tohave an elongated opening for the area of intense illumination and if sothe construction of Figs. 5 and 6 may be used. Here the filament,cathode, and cathode supporting parts are identical with those alreadyshown and described with the exception of the housing which has in itsfront an elongated slot 3| instead of the hole as shown in the housing23. 7 The control electrode 32 is similar to the control electrode shownin Fig. 1 but has an opening 33 corresponding in shape tothe opening ilin the housing 33. In like manner the anode 53 com prises a plate withan elongated slot 33 therein so that the slot Si in the housing 58 maybe seen through it.

In assembling the construction of Figs. 1 to 4 inclusive the filament isfirst welded to the support rod 21 and then the member I! is placed overthe filament. The cathode is placed over the filament and the cathodeband 38 welded to its support rod 3| The housing 20 is then placed overthe cathode and over the member l5 and the housing clamps 2| are weldedto the support rods 23 to hold the whole unit in position. The controlelectrode and anode may then be mounted in position as indicated. Theconstruction shown in Figs, 5 and 6 may be assembled in the same manner.

In Figs. 7, 8 and 9 I have shown another embodiment of the invention inwhich the insulating refractory housings 28 and 58 of Figs. land 5 areeliminated and the control electrode itself becomes the housing forpreventing the discharge between the cathode and anode except through apredetermined opening. This device is shown mounted in a bulb 58 havinga press 51 somewhat similar to the press ll of the preceding figures andhaving a similar circular extension 58 at the center thereof whose topis flush with the top of the press i I.

A heating filament 59 may be supported on a pair of support rods 50which are sealed in the press 51 at about the center thereof and thisheater may be surrounded by a cylindrical cathode Gi similar to thecathode I 3 of the preceding figures and coated with electron emittingmaterial in a similar manner. the cathode 6| may be provided with asecuring band 62 of metal which may be welded to a support rod 63 alsosealed in the press 51 adjacent the filament supports 88. A sleeve 64 ofinsulatlng material having a diameter large enough to surround thecathode support rod G3 as well as the filament supports 60 is providedresting upon the surface of the enlarged portion 58 of the press 51. Adisc 65 also made of insulating material may be placed on top of thesleeve 54, a suitable hole 68 being provided in the center thereof toreceive the cathode while a flange 61 may also be provided in the outerperiphery to fit over the upper edge of the sleeve 64.

I provide a control electrode 68 preferably of a refractory metal suchas tungsten or molybdenum in a tubular form to surround the cathode.Thus a pair of plates 69 may be pressed to form a semi-cylindricalportion with a flange 10 at each side thereof. The two plates are placedtogether with the concave sides adjacent flanges 10 may be welded. Thisholds the disc 65 and the sleeve 64 securely in place upon the top ofthe press. The upper end of the control electrode 68 is closed by meansof an insulating disc 14 which fits down inside of the electrode 68 andis provided with a recess 15 to receive the top of the cathode, thusspacing the cathode at the top from the control element. The disc 14 isheld in place by suitable lugs 11 which may The lower end of be formedon the upper edge of the control element 88 and which are then bent overon top of the disc ll as shown.

The control element 88 may have a small hole 18 in the side thereof andan anode 19 may be placed directly in front of this hole and supportedupon a pair of support rods 88 which may be sealed in the press 51 ateach side of the sleeve 84. The anode is provided with a hole 8i whichis larger in diameter than the hole 18 in the control element so thatthe intense light passing through this hole will be evidenced as viewedthrough the hole in the anode.

In assembling the device just described the filament is first welded tothe support rods 60 and the cathode is then slipped over the filamentand welded to the support rod 63. Then the sleeve 04 is placed over thecathode and filament upon the top of the press and also the disc 65 isplaced over the cathode to rest on top of the sleeve, and the controlelement 68 is slipped down over the cathode, the support rods I2 passingthrough the grooves II provided for that purpose in the flanges 18. Thecontrol element is then welded in'place by welding the flanges 10 to thesupport rods I2. This holds the insulating sleeve and insulating disc inposition and the insulating disc 14 is then positioned on top of thecathode inside of the control element 88 and the flanges 'II bent over,which holds it in position and spaces the cathode from the controlelement.

The device just described works similarly to the devices of Figs. 1 to 6inclusive. As the con trol element itself is also the shield it willprevent any discharge from passing to the anode except through theopening in the side thereof and hence the intense illumination willappear at this opening.

In some instances it may be desired to protect the edges of the opening18 in the control electrode against the intense heat produced by thedischarge passing therethrough. In Fig. 8a a construction to accomplishthis purpose is shown in which the hole 18a in the control electrode ismade somewhat larger with a slot 18b at one side thereof. A bushing 19aof some highly refractory non-metallic material may be inserted in thehole 18a, a suitable lug 19b being provided on the outer end of thebushing to hold it in place when the bushing is rotated in the hole. Thehole through the bushing should have the same diameter as the hole 18 inthe control electrode described above but as the bushing can stand ahigher temperature than the metal of the electrode there is less dangerof the edges of the opening melting or otherwise being destroyed by theheat or discharge.

If it is desired to have an elongated slot for the opening theconstruction shown in Figs. 9 to 14 may be employed. Here the press,cathode, and filament construction are the same and the sleeve 64 isemployed to surround the filament and cathode support posts as in theconstruction just described. The control electrode 82, however, isformed of two plates which are bent in a semi-cylindrical form but whichare provided with a flange 83 at one side only so that the edges of thesemi-cylindrical plates where there is no flange form the opening 85through which the light and discharge pass. The control element issupported upon one support rod 86 only, which is positioned at theextreme end of the press 81 opposite the anode end and to which theflanges 83 are welded similarly to the manner described in connectionwith Fig. 7. However, the

insulating disc 88 at the bottom is provided in addition to the hole 88for the cathode with a suitable groove 88 in which the bottom of thecontrol element may fit. A radial groove II in 5 the side of the member88, (see Fig. 13), communicating with the groove 88 permits the flanges88 to extend outwardly toward the support rod 88. The disc may also havea depending flange 82 for fitting over the sleeve 84. This construc- 10tion holds the two sides of the control element firmly and preventswarping due-to variations of heat and cold so that the slot 88 throughwhich the discharge passes will not open or close.

The top of the control element is held in a 16 similar way by a disc 83which'is provided with the grooves 80 and 8|, shown in the disc 88, anda recess 84 in the center to receive the upper end of the cathode. Thedisc 83 is also provided with a plurality of notches 88 into which lugs81 20 attached to the control element may pass and be bent over the topof the disc thereby holding the disc securely to the control element andspacing the cathode therefrom at the top.

The anode may comprise a plate 98 mounted 25 upon a support rod 88 whichis sealed in the press 81 opposite to the support rod 86. The plate 88may be provided with an elongated slot I which is slightly larger thanthe slot 85 in the control element.

30 If desired the opening through the control electrode may be providedwith refractory edges to prevent destruction by the intense heatsimilarly to the construction described in connection with Fig. 8a.

35 The elements of this device are assembled similarly to that shown inFigs. 7, 8, and 9 and no description of the assembly thereof is believedto be necessary.

It will be seen from the above that I have pro- 40 vided a lamp thelighting energy of which is obtained from a source entirely independentof the incoming modulation signal and that the light produced by thelamp will be varied in accordance with a very minute voltage modulationwhich is 45 impressed upon a suitable control electrode. This is a greatadvantage over lighting devices where the energy for producing the lightis derived from the modulating light signal inasmuch as in the presentinvention the intensity of the light 50 may be enormously increased overany of these prior art devices. It is also. possible to eliminate thenecessity of a powerful incoming modulated signal as the control elementof my device will respond to very minute changes in incoming volt- 55age and hence it is not necessary to amplify an incoming signal as forinstance a television signal to any great extent thereby producing amore true reproduction of the signal as it eliminates 'the inherentdistortion usually accompanying large amplification.

In the several embodiments of the invention I have shown one form of theanode as comprising a plate of metal but it will be understood that anymetallic electrode may be used to act as an 65 anode such as a singlewire, for instance, which is positioned in front of the openingthroughwhich the discharge passes. It is desirable, however, to

make the anode large enough so that it will not overheat inasmuch as thetemperature thereof is raised considerably by bombardment and a smallwire, for instance, may become white hot when subject to the discharge.In like manner the control electrode of Figs. 1 to 6 inclusive may bemade of wire mesh if desired or formed of a plate, the importantrequirements being that the control electrode be near the openingthrough which the discharge passes and large enough to aifect thepotential of the region immediately adiacent to such opening. When thefilament has been shown as connected to the secondary of a transformerand perhaps preferably adapted to operate on a low voltage it will beevident that it may be designed to operate on any desired voltage ashigh as 110 or higher.

While the invention has been shown and described particularly inconnection with a lamp used for television reproduction it is to beunderstood that the invention is not limited to television use but maybe employed wherever it is desired to modulate a source of light as forsound-on-fllm recording or any type of signal work.

Many modifications of the invention may be resorted to without departingfrom the spirit thereof and I do not, therefore, desire to limit myselfto what has been shown and described except as such limitations occur inthe appended claims.

What I desire to claim and secure by Letters Patent is:

1. In a device of the class described an envelope,

a press within said envelope, a cathode moimted on said press, means toheat said cathode, an anode spaced from said cathode, a controlelectrode positioned between said anode and cathode, and a shieldbetween said cathode and anode, and oathode and control electrode, andhaving a small opening in the vicinity of said control electrode.

2. In a device of the class described an envelope, a press within saidenvelope, a cathode mounted on said press, means to independently heatsaid cathode, a shield completely surrounding said cathode only, saidshield having a small opening in the side thereof, an anode positionedin front of said opening, a control electrode positioned between saidanode and cathode, and an ionizable gas within said envelope. 5o

3. In a device of the class described an envelope,

a press within said envelope, a cathode mounted upon said press,independent means to heat said cathode, a shield completely surroundingsaid cathode, said shield having a small aperture in one side thereof,an anode positioned directly in front of said aperture, said anodehaving an opening therein slightly larger than the aperture in saidshield and in alignment therewith, and an electrostatic controlelectrode positioned between said anode and cathode, and between saidanode and shield, and removed slightly from the com-- mon axis of theopening in said anode and the aperture in said shield, and an ionizablegas with- 55 in said envelope.

CHESTER H. BRABEL'IUN.

